City | 2024 Population |
|---|---|
| Oak Grove | 1,562 |
| Oakland City | 2,251 |
| Oaktown | 585 |
| Oakville | 444 |
| Odon | 1,379 |
| Ogden Dunes | 1,170 |
| Ohio | 1,834 |
| Oil | 2,575 |
| Oldenburg | 649 |
| Olive | 3,388 |
| Ontario | 856 |
| Onward | 77 |
| Oolitic | 1,134 |
| Ora | 294 |
| Orange | 673 |
| Orangeville | 715 |
| Oregon | 1,830 |
| Orestes | 340 |
| Orland | 395 |
| Orleans | 2,058 |
| Osceola | 2,595 |
| Osgood | 1,596 |
| Osolo | 28,723 |
| Ossian | 3,397 |
| Oswego | 650 |
| Otisco | 222 |
| Otsego | 2,506 |
| Otter Creek | 1,360 |
| Otter Lake | 782 |
| Otterbein | 1,125 |
| Otwell | 256 |
| Owen | 996 |
| Owensburg | 75 |
| Owensville | 1,334 |
| Oxford | 1,166 |